Glossary of Molecular Imaging Terms

A

﻿Alzheimer’s disease

An irreversible, progressive brain neurodegenerative disorder that slowly destroys memory and thinking function. AD, the most common form of dementia, begins deep in the brain where healthy neurons begin to work less efficiently and eventually die. This process gradually spreads to the brain’s learning and memory center—the hippocampus—and other areas of the brain, which begin to shrink. At the same time, beta-amyloid plaques begin to multiply throughout the brain.

amino acid

An organic compound containing nitrogen, carbon, hydrogen and oxygen; one of the 20 building blocks of protein.

aneurysm

A balloon-like bulge in an artery. An aneurysm can grow large and rupture–or burst–or dissect, which occurs when one or more layers of the artery walls splits. Both cause internal bleeding and can be fatal.

angiography

An imaging study that is used to evaluate patients for coronary artery disease. The procedure involves inserting a catheter into the body and threading it into the aorta.

annihilation

The process of a particle and its corresponding anti-particle (a particle with the same mass but opposite electric charge) combining to produce energy in the form of photons.

antibody

A protein produced by the body’s immune system in response to the presence of a foreign substance, called an antigen. The body fights off infection by producing antibodies, which destroy or neutralize bacteria, viruses, or other harmful toxins.

antigen

Any foreign substance, such as a protein, toxin or other particle that stimulates the body’s immune system to produce antibodies. Antigens can be substances like bacteria, viruses, or even pollen that invade the body.

arrhythmia

Arrhythmias are also called heart rhythm problems. A disorder of the heart rate or heart rhythm. Arrhythmias occur when the heart that beats too fast (called tachycardia), too slow (called bradycardia), or irregularly.

atherosclerosis

A disease in which fatty deposits consisting of fat, cholesterol and other substances collect along the walls of arteries. It is sometimes referred to as hardening of the arteries, arteriosclerosis and coronary artery disease.

atrophy

Shrinkage.

automated external defibrillator

A device used on an individual whose heart suddenly and unexpectedly stops beating. An AED sends an electric shock to the heart in an effort to restore its normal rhythm.

automatic internal cardiac defibrillator

A device to prevent sudden cardiac death that is surgically placed under the skin in the chest or abdomen. When the AICD detects an irregular arrhythmia, the device uses electric pulses or shocks to restore the heart’s normal rhythm.

axillary lymph node dissection

The surgical removal of up to 30 lymph nodes from the armpit area so they may be examined under a microscope for evidence of cancer.

axillary lymph nodes

Lymph nodes that are located in the axillary, or armpit, area.

axillary lymph nodes, dissection

Lymph nodes found in the underarm region (axilla). In an axillary lymph node dissection, the lymph nodes under the armpit are explored and removed as a part of breast cancer surgery. Some or all of these lymph nodes are examined under a microscope by a pathologist to see if cancer cells are present.

axon

A long, slender projection from a nerve cell, or neuron, which conducts electrical impulses away from the cell.

B

benign

A process or a growth in the body, or in an organ, that is not cancerous. Also called non-malignant.

beta-amyloid plaque

Thick deposits of proteins in the brain considered one of the hallmarks of Alzheimer’s disease (AD).

biological pathway

The molecular interaction involved in biological processes; often a cascade of actions among molecules in a cell that leads to a product or outcome.

bioluminescent imaging

One of two major types of optical imaging, in which light-producing molecules designed to attach to specific cells such as cancer cells or brain chemicals are injected into the patient’s bloodstream. Imaging is then performed using devices that are able to detect these molecules inside the body. Bioluminescent imaging uses natural chemicals such as luciferase, the substance that enables fireflies to glow, to trace the movement of certain cells or to identify the location of specific chemical reactions within the body.

biomarker

A molecule or substance in the body that is used as an indicator of a specific biological process occurring in the body. The most common use is to find indications of disease. For example, the presence of prostate specific antigen (PSA) in the body is a marker for prostate disease.

biopsy

The process of removing a small amount of tissue from the body for examination under a microscope.

bipolar disorder

Also called manic-depressive disorder. A mental disorder that causes mood swings that range from of the lows of depression to the highs of mania.

blood-brain barrier

A separation between the circulating blood and cerebrospinal fluid that selectively prevents substances from passing out of the blood stream into brain tissue and cerebrospinal fluid.

bone marrow

The soft, spongy tissue, found in the hollow interior of bones, that produces white blood cells, red blood cells and platelets.

bone scan

A diagnostic imaging test in which radioactive material called a radiotracer when injected into the patient’s bloodstream accumulates predominantly in the bones and can be detected by an imaging device. The resulting two-dimensional or three-dimensional images can reveal various processes such as bony fractures, infection, inflammation and changes secondary to presence of cancer cells.

bradycardia

A type of arrhythmia, or heart rhythm problem, that occurs when the heart beats too slow.

breast-specific gamma imaging

Also called molecular breast imaging. A diagnostic procedure performed as a follow-up study to a mammogram that detects cancer or is inconclusive in its findings. BSGI is used to detect additional lesions missed by mammography or physical exam as well as cancers that are difficult to detect using mammography.

Breast-specific gamma imaging

A diagnostic procedure performed as a follow-up study to a mammogram to detect additional lesions missed by mammography and physical exam and cancers that are difficult to detect using mammography. The procedure involves the use of a radiotracer that is injected into the patient’s bloodstream and accumulates in malignant tissue where it can be detected by a special gamma camera modified for breast imaging.

C

C-11-PIB

Carbon-11-labeled-Pittsburgh Compound B (C-11 PIB), also known as PIB, an imaging agent or probe used in brain imaging to bind to the abnormal plaques associated with Alzheimer’s disease and so they can be visualized on a PET scan.

carcinoembryonic antigen (CEA)

A protein normally found in small amounts in the blood and in fetal tissue. It is also produced by some types of tumors, including some breast and gastrointestinal cancers, making it a tumor marker, or an indication that disease may be present on molecular images. Colorectal cancer is the most common cancer that raises the level of this tumor marker in the blood.

cardiac catheterization

A procedure in which a catheter, a thin flexible tube, is passed into the right or left side of the heart. This procedure can be used to obtain information about the heart and its blood vessels or to provide treatment for heart conditions, such as a blockage in an artery.

cardiac sarcoidosis

A chronic and inflammatory autoimmune disease that affects the heart. The disease causes clumps of cells similar to scar tissue to grow in the heart muscle and interfere with heart function.

cardiomyopathy

A weakening of the heart muscle or change in the structure of the heart muscle structure. A chronic condition, it is often associated with heart function problems.

cartilage

Dense connective tissue found in many parts of the body, primarily in association with bony joints and interfaces.

cervix

The lower part of the uterus, connecting the uterus with the vagina; pertaining to the cervix.

chemotherapy

A systemic treatment for cancer that involves the use of chemical agents to destroy or stop cancer cells from growing. Systemic treatment affects all cells of the body.

co-registration

The combining of the two different imaging techniques allowing information from two different studies to be viewed as a single set of superimposed images. e.g. PET and CT.

colorectal

Pertaining to the colon, the longest part of the large intestine or the rectum, the terminal continuation of the colon.

colorectal cancer

Cancer that occurs in the colon (part of the large intestine) or the rectum.

computed tomography

A medical imaging technique that uses a computer to acquire a volume of x-ray based images, generally reconstructed as two-dimensional (2D) or three-dimensional (3D) pictures of inside the body. These images can be rotated and viewed from any angle. Each CT images is effectively a single ‘slice’ of anatomy.

congenital

Present from birth.

Congestive heart failure

Also called heart failure. A condition in which the heart can no longer pump enough blood or meet the body’s needs for blood and oxygen, especially when the patient is active or exercising. Congestive heart failure is a chronic, long-term condition that may affect the right, left, or both sides of the heart. There are two types of heart failure:

systolic, when the heart muscle cannot pump, or eject, enough blood out of the heart.

diastolic, when the heart muscle is stiff and does not allow the heart to fill up with blood easily.

contrast agent (contrast media or contrast material)

A compound or other substance introduced into the body in order to create a difference in the apparent density of various organs and tissues, making it easier to see, or delineate body tissues and organs.

coronary artery disease

A condition involving the narrowing of the coronary arteries that carry blood and oxygen to the heart muscle.

cryosurgery

A procedure that uses liquid nitrogen to freeze and destroy cells; it may be used to treat melanoma.

D

degenerative

Progressively deteriorating over time. In degenerative disease, the function or structure of the affected tissues or organs gets worse as time progresses.

dementia

A general term for memory loss and decline in intellectual functioning that is severe enough to interfere with an individual’s ability to perform routine tasks.

diagnostic imaging (diagnostic scan)

Diagnostic imaging uses technologies such as x-ray, CT, MRI, ultrasound, PET and SPECT to provide physicians with a way to look inside the body without surgery. Diagnostic imaging is considered a non-invasive diagnostic technique, as opposed to a biopsy or exploratory surgery. PET, SPECT and some types of MR imaging also provide information about how certain tissues and organs are functioning.

diastolic

Refers to the filling of the heart with blood between muscle contractions. In diastolic heart failure, the heart muscle becomes stiff and does not allow the heart to fill up with blood easily.

differential diagnosis

The process of distinguishing between two or more diseases or conditions that feature identical or similar symptoms. A doctor commonly performs a differential diagnosis to rule out other possibilities.

differentiated thyroid cancer

A type of cancer of the thyroid gland. Differentiated thyroid cancers include papillary, follicular and Hürthle cell thyroid cancers. The cells of these cancers appear similar to normal thyroid tissue when looked at under a microscope.

diffuse

Spread out.

ductal carcinoma in situ (DCIS)

A breast cancer that has not spread beyond the lining of the milk ducts into the surrounding breast tissue.

ducts

Tubes that carry a substance from one region of the body to another. e.g. tubes that carry milk from glandular tissue to the nipples of the breast.

E

ECG stress test

Also called exercise treadmill testing. A type of stress test performed to help diagnose coronary artery disease by providing information on how the heart works during physical stress.

The test is performed by placing electrodes on the patient’s chest that are attached to an electrocardiography (ECG) machine that measures the electrical activity of the heart. The ECG records the heart rate and rhythm, as well as the strength and timing of electrical signals as they pass through each part of the heart during rest and exercise.

echo stress test

Also called stress echocardiography. An exam often performed after an a patient has undergone an exercise stress test and received abnormal results. The patient undergoes echocardiography, which uses sound waves to create a moving picture of the heart, while at rest and immediately following exercise.

echocardiography

An imaging technology that uses sound waves to create a moving pictures of the heart. Echocardiography is part of an echo stress test in which the heart is imaged at rest and immediately following exercise in order to help diagnose coronary artery disease.

ejection fraction

The fraction of blood pumped out of the right and left ventricles with each heart beat.

electrocardiography

A procedure in which a special machine connected to electrodes that are placed on a patient’s chest measures the electrical activity of the heart.

electrodessication and curettage

A type of surgical procedure used to treat melanoma that involves alternately scraping and burning the tumor.

electromagnetic radiation

A spectrum of energy, demonstrating the phenomenon of self-propagating waves, and both electric and magnetic fields. Visible light, radio waves, gamma rays, and x-rays, are all within the spectrum of electromagnetic radiation. The subdivisions are a function of differences in frequency and wavelength. Photons, an often used unit of energy within the molecular imaging realm, is part of this spectrum.

electron

A subatomic particle that carries a negative charge. An electron orbits and is bound to the nucleus of an atom by electromagnetic forces.

embolism

An obstruction within an artery, typically by a clot of blood or an air bubble.

endocrine

Any of various glands, including the thyroid, adrenal, and pituitary glands, that secrete hormones or other substances into the blood or lymph.

enzyme

Any of several complex proteins that are produced by cells and act as catalysts in specific biochemical reactions.

epilepsy

Epilepsy is a brain disorder in which the patient experiences repeated, unpredictable seizures, or episodes of disturbed brain activity that cause changes in attention or behavior.

esophageal

The tube that carries food, liquids and saliva from the mouth to the stomach; relating to the esophagus.

estrogen receptor-positive breast cancer

Unlike normal breast cells, cancer cells arising in the breast do not always have receptors for estrogen, the hormone that typically acts on breast tissue.

Breast cancers that DO have estrogen receptors are said to be “estrogen receptor-positive,” while those breast cancers that DO NOT possess estrogen receptors are “estrogen receptor-negative.” In women with estrogen receptor-positive cancers, cancer cell growth is under the control of estrogen. Therefore, such cancers are often susceptible to treatment with tamoxifen (Nolvadex®), because tamoxifen works by blocking the interaction between estrogen and the estrogen receptor. In contrast, the growth of estrogen receptor-negative cancer cells is not governed by estrogen and is not treated with tamoxifen.

estrogen, estrogen receptor

Estrogens are molecules that stimulate the development and maintenance of female characteristics and sexual reproduction. The most prevalent forms of human estrogen are estradiol and estrone. Both are produced and secreted by the ovaries, although estrone is also made in the adrenal glands and other organs.

Estrogens are signaling molecules, or hormones, that travel throughout the bloodstream and interact with certain cells in target tissues. The breast and the uterus are two of the main targets of estrogen, as are the brain, bone, liver, and heart. Estrogens act on these target tissues by binding to parts of cells called estrogen receptors.

An estrogen receptor is a protein molecule found inside cells targeted for estrogen action. Only estrogens (or closely related molecules) can bind to these receptors.

Exercise treadmill testing

Also called ECG Stress Test. A type of stress test performed to help diagnose coronary artery disease by providing information on how the heart works during physical stress.

The test is performed by placing electrodes on the patient’s chest that are attached to an electrocardiography (ECG) machine that measures the electrical activity of the heart. The ECG records the heart rate and rhythm, as well as the strength and timing of electrical signals as they pass through each part of the heart during rest and exercise.

F

FDG

18F-fluorodeoxyglucose (FDG). May also be referred to as Fluorine-18 or F-18 FDG. A frequently used radiotracer in PET scanning. FDG is a compound in which the radioactive isotope fluorine-18 is attached to a molecule of glucose, or sugar. Once in the body, the FDG is absorbed by various tissues is detected by a PET scanner. Images that show how the radiotracer is distributed within the body, which help physicians assess how well the body is functioning and diagnose various medical conditions.

fluorescence imaging (fluorescent molecular tomography [FMT])

One of two major types of optical imaging in which light-producing molecules designed to attach to specific cells such as cancer cells or brain chemicals are injected into the patient’s bloodstream. Imaging is then performed using devices that are able to detect these molecules inside the body. Fluorescence imaging uses proteins that produce light when activated by an external light source, such as a laser, to trace the movement of cells or identify the location of chemical reactions in the body.

fluorine

The chemical element represented by the symbol F and the atomic number 9. A radioactive fluorine atom is attached to a molecule of glucose or sugar to create the radiotracer FDG, used in positron emission tomography.

fluoroestradiol (FES)

16-alpha-[18F]-fluoroestradiol (FES) is a new radiotracer for PET scanning under development. FES allows researchers to image the estrogen receptors on cells in the breast. FES PET may allow researchers to better understand why hormonal therapy is not effective in some women with estrogen-positive breast cancer (ER+) — and to predict which patients with ER+ cancer will respond to hormonal therapy.

fluorothymidine (FLT)

[18F]-3′-deoxy-3′-L-fluorothymidine. A new radiotracer under development for PET scanning to image tumor proliferation, or growth. In breast cancer patients, PET scanning with FLT may indicate — early in the treatment process — when chemotherapy is working and help assess the effectiveness of new drugs in clinical trials.

follicular thyroid cancer

One of several types of thyroid cancer; it may be identified and staged with low-dose I-123, and potentially treated with I-131 radiotherapy.

frontotemporal dementia

A group of rare brain disorders that involves the shrinking (atrophy) of tissues in the frontal and temporal lobes of the brain. Pick’s disease is an example of this type of dementia.

frontotemporal disorders

An umbrella term for a diverse group of uncommon disorders that primarily affect the frontal and temporal lobes of the brain — the areas generally associated with personality, behavior and language–causing them to shrink or atrophy.

fusion imaging

The combination of the two imaging techniques that allows information from two different studies to be viewed in a single set of images.

G

gallbladder

The small sac-shaped organ beneath the liver, in which bile is stored after secretion from the liver and before it is released into the intestine.

gamma camera

A specialized camera that is capable of detecting gamma rays- the byproduct of a radiotracer, which is a combination of a radioactive atom, called an isotope, and another substance. The gamma camera creates two-dimensional pictures of the inside of the body from different angles.

gastric

Relating to or involving the stomach.

gastrointestinal (GI) tract

A long twisting tube within the human body along which food passes for digestion. The GI tract includes the esophagus, stomach, small intestine, large intestine, rectum and anus.

glial cell

The brain is largely made up of two cell types: neurons and glial cells. Glial cells support the various processes involved in moving messages between neurons.

gynecology

The study and medical treatment of the diseases of women, in particular those affecting the reproduction system and urinary tract. Pertaining to gynecology.

H

Heart attack

Also called myocardial infarction. A medical emergency in which the vessels that supply oxygenated blood to the heart become blocked, the part of the heart muscle starved for oxygen may die or become permanently damaged.

Heart failure

Also called congestive heart failure. A condition in which the heart can no longer pump enough blood or meet the body’s needs for blood and oxygen, especially when the patient is active or exercising. Congestive heart failure is a chronic, long-term condition that may affect the right, left, or both sides of the heart. There are two types of heart failure:

systolic, when the heart muscle cannot pump, or eject, enough blood out of the heart.

diastolic, when the heart muscle is stiff and does not allow the heart to fill up with blood easily.

hippocampus

A part of the brain that plays a central role in many functions, including the processing of memories.

Hodgkin’s disease

Also known as Hodgkin’s lymphoma (HL), one of two types of lymphoma or cancer of the lymphatic system, which includes the lymph nodes, spleen, thymus and bone marrow.

Hurthle cell thyroid cancer

One of several types of thyroid cancer; it may be treated with high-dose I-131 radiotherapy.

hybrid imaging

The combination of the two imaging techniques that allows information from two different studies to be viewed in a single set of images.

hypothyroidism

A condition in which the thyroid gland is not making enough thyroid hormone, hormones that control the way the body uses energy.

I

I-123 MIBG scintigraphy

I-123-MIBG scintigraphy is an imaging test used to detect neuroendocrine tumors.The procedure involves the injection of the radiotracer I-123-MIBG into the patient’s bloodstream and imaging with a gamma camera or SPECT.

I-131 radiotherapy

A treatment for hyperthyroidism, thyroid cancer and lymphoma in which radioactive iodine I-131 is delivered directly to thyroid or cancer cells in order to destroy them.

imaging agent (imaging probe, radiotracer)

A substance introduced into the body as part of a diagnostic procedure. In nuclear medicine, imaging agents are typically a compound consisting of a drug or a natural substance, such as glucose, and a small amount of radioactive material, which can be detected by an imaging device to produce pictures of the inside of the body.

imaging biomarker (see biomarker)

Imaging biomarkers are measurable characteristics obtained by imaging that indicate a specific biological process is occurring in the body. They help speed drug development because the biomarkers show effectiveness earlier than anatomic changes. They have been historically difficult to use in drug trials and clinical practice due to a lack of standardized methods and regulatory approval.

imaging device

A technological apparatus used to produce detailed images of the inside of the body for diagnostic or therapeutic purposes. In molecular imaging, examples of these devices include the gamma camera, PET scanner, MRI unit, optical imaging detector, and ultrasound machine.

imaging probe (imaging agent)

A molecule that can bind both to a radiotracer and to a molecule of interest, such as cancer cells, within the body so that they may be imaged with molecular imaging technologies.

immunotherapy

A treatment that imitates cellular activity in the body’s immune system in which white cells recognize invading organisms and respond by secreting a protein substance called an antibody that hones in on an antigen on foreign cells, allowing other white cells to destroy it. In immunotherapy, scientists create monoclonal antibodies in a laboratory that are designed to recognize and bind to the antigen of a specific cancer cell. When the antibodies are combined with a radioactive material (called radioimmunotherapy) and injected in a patient’s bloodstream, the antibody travels to and binds to cancer cells allowing a high dose of radiation to be delivered directly to the tumor.

incidental cancers

Unexpected cancerous lesions identified by diagnostic imaging tests in addition to different primary disease being investigated.

indium-111-octreotide

A radiopharmaceutical being evaluated in clinical trials as an alternative to radioiodine for patients whose thyroid cancer is not responsive to I-131 radiotherapy with iodine.

intravenous (IV)

Within or by means of a vein.

ionizing radiation

Subatomic particles or electromagnetic waves that are energetic enough to detach electrons from atoms or molecules, a process called ionization. Radiation on the short-wavelength end of the electromagnetic spectrum, such as x-rays and gamma rays are ionizing. Ionizing radiation is produced by radioactive decay, nuclear fission and nuclear fusion and by particle accelerators.

isotope

Atoms of a single element that have differing masses. Isotopes are either stable or unstable (radioisotope). Radioisotopes are radioactive: they emit particulate (alpha, beta) or electromagnetic (gamma) radiation as they transform or decay into stable isotopes.

L

larynx

Also called the voicebox. An organ in the respiratory system, primarily composed of cartilage, and located just below the pharynx in the neck. It contains the vocal cords.

Lewy body dementia

The second most common type of progressive dementia after Alzheimer’s disease and a cause of a progressive decline in mental abilities, visual hallucinations, significant fluctuations in alertness and attention and rigid muscles, slowed movement and tremors. This form of dementia is characterized by abnormal round structures — called Lewy bodies — that develop in regions of the brain involved in thinking and movement.

ligand

In medical imaging, ligands are molecules that can bind both to a tracer (radioactive or light emitting) and to a molecule of interest within a living system. For example, in radioimmunotherapy a radioisotope is attached to a monoclonal antibody. The antibody is the ligand; it is designed to bind with specific molecules on the surface of cancer cells, so it carries the radioisotope to the tumor. The radiation kills the cancer cell while sparing nearby tissue. In optical imaging, the ligand might carry a bioluminescent protein. The antibody binds to a receptor on the surface of the cell being studied, delivering the bioluminescent protein directly where the researcher wants it.

lobules

A small lobe or part of a gland.

localize

To identify the location of or to accumulate in a specific location.

lumpectomy

A surgical procedure to remove a tumor and surrounding tissue from the breast.

lymph

A clear, watery fluid that contains white blood cells, plasma and other substances and is transported throughout the body in tubes known as lymph vessels. Lymph is collected from tissues throughout the body, flows through vessels and lymph nodes, and is eventually added to the bloodstream.

lymph node biopsy

The removal of all or part of a lymph node to be examined under a microscope for evidence of cancer cells.

lymph nodes

Small, bean-shaped organs located in various areas of the body along throughout the lymphatic system, a network of organs, lymph nodes and vessels that removes lymph fluid from the tissues of the body and returns it to the blood stream.

Thin tubes that carry lymph through the lymphatic system. They branch, like blood vessels, into all parts of the body.

lymphatic system

A network of organs, lymph nodes and vessels that removes lymph fluid from the tissues of the body and returns it to the blood stream. A major component of the body’s immune system that makes and stores cells needed to fight infection and diseases such as cancer.

lymphocyte

A type of white blood cell formed in lymph nodes, the spleen, and bone marrow. The main types of lymphocytes are T and B-lymphocytes.

lymphoma

Cancer of the lymphatic system, which includes the lymph nodes, spleen, thymus and bone marrow. There are two types of lymphoma: Hodgkin’s lymphoma (HL) or disease and non-Hodgkin lymphoma (NHL).

lymphoscintigraphy

A procedure that uses a radiotracer and gamma camera to produce images of the lymphatic system to help identify the first, or sentinel, lymph nodes into which a cancer site drains.

M

magnetic resonance imaging (MRI)

Magnetic resonance imaging (MRI) uses a powerful magnetic field, radio frequency pulses and a computer to produce detailed pictures of organs, soft tissues, bone and virtually all other internal body structures. The diagnostic imaging study helps physicians diagnose and treat medical conditions. A special type of MRI called MR spectroscopy, measures the concentration of metabolites, which are substances produced by chemical reactions in the brain and other areas of the body.

magnetic resonance spectroscopy (MRS)

MR spectroscopy (MRS) is a variation of conventional magnetic resonance imaging (MRI). A diagnostic imaging exam, MRS measures the concentration of metabolites, which are substances produced by chemical reactions in the brain and other areas of the body.

malignant

Cancerous cells able to grow into surrounding tissue, spread to other parts of the body and destroy normal cells.

masectomy

Surgical removal of the breast, usually to remove cancerous tissue.

matrix metalloproteinase (MMP)

An enzyme whose activation levels are imaged with PET to help assess changes in the size, shape, and function of the heart after injury such as a heart attack to (called ventricular remodeling).

mediastinoscopy

A surgical procedure performed to determine whether non-small cell cancer has spread to the lymph nodes in the chest cavity. PET-CT guidance may be used to identify the lymph nodes most likely to contain cancer cells.

melanin

Pigment produced by skin or melanocyte cells that give the skin a darker hue.

melanocytes

Cells throughout the skin that produce pigment called melanin that makes the skin tan.

melanoma

The third most common form of skin cancer that begins in melanocytes, the cells throughout the skin that produce pigment called melanin that makes the skin tan.

metabolic

Part of metabolism, the set of chemical reactions that occur in living organisms to convert fuel into energy.

metabolism

The set of chemical reactions that occur in living organisms to convert fuel into energy.

metabolites

Any substance produced by or involved in a chemical reaction that is part of metabolism.

metastasize

The spread from one part of the body to another, as in cancer cells.

micro- (PET, MR, CT, SPECT)

Medical imaging instruments or techniques specifically designed for medical research using small animals. Micro-imaging studies are useful in preclinical investigations of new imaging agents or with existing imaging agents to evaluate new therapies using exiting agents in animal models.

microbubbles

Extremely small hollow structures either containing or attached to therapeutic or imaging molecules. They are used clinically with ultrasound as a contrast agent.

mild cognitive impairment (MCI)

A condition in which memory or other cognitive functions are below normal but do not interfere with daily functioning. MCI is considered a transitional state between normal forgetfulness and dementia.

millisieverts (mSv)

A measure of radiation dose.

molecular imaging (MI)

Molecular imaging is an array of non-invasive, diagnostic imaging technologies that can create images of both physical and functional aspects of the living body. It can provide information that would otherwise require surgery or other invasive procedures to obtain. Molecular imaging differs from microscopy, which can also produce images at the molecular level, in that microscopy is used on samples of tissue that have been removed from the body, not on tissues still within a living organism. It differs from X-rays and other radiological techniques in that molecular imaging primarily provides information about biological processes (function) while CT, X-rays, MRI and ultrasound, image physical structure (anatomy).

An imaging biomarker that is molecule based, as opposed to being a single atom or an ion. e.g. fragments of DNA, or an antibody

molecular radiotherapy (MRT)

A treatment for cancer. MRT is a systemically administered, targeted therapy that delivers radiation at the cellular and molecular level.

molecular ultrasound

The use of targeted microbubbles, extremely small, hollow structures that serve as a contrast agent during an ultrasound exam.

monoclonal antibody

A substance created in a laboratory that is designed to recognize and bind to the antigen of a specific cancer cell when introduced into the body. When these antibodies are combined with a radioactive material and injected in a patient’s bloodstream, (a treatment called radioimmunotherapy) the antibody travels to and binds to cancer cells allowing a high dose of radiation to be delivered directly to the tumor.

monoclonal antibody imaging

The use of a laboratory-developed molecule called a monoclonal antibody that is designed to attach to specific cancer cells in order to produce pictures of a tumor inside the body. Once the monoclonal antibody is combined, or labeled, with a radioactive atom and injected into the patient, single-photon emission computed tomography (SPECT) imaging is performed, creating three-dimensional images of the tumor.

MR spectroscopy

MR spectroscopy (MRS) is a variation of conventional magnetic resonance imaging (MRI). A diagnostic imaging exam, MRS measures the concentration of metabolites, which are substances produced by chemical reactions in the brain and other areas of the body.

myelin

A white, fatty material that surrounds the axons of nerve cells.

myocardial infarction (MI)

Also called a heart attaack. A medical emergency in which the vessels that supply oxygenated blood to the heart become blocked, the part of the heart muscle starved for oxygen may die or become permanently damaged.

myocardial perfusion imaging

A study that assesses heart function and whether the heart is receiving enough blood and oxygen. A physician may perform a MPI study to help diagnose symptoms of coronary artery disease (CAD), such as shortness of breath or chest pain; heart rhythm problems; or to evaluate or plan treatment for a heart condition.

MPI scans are created with either SPECT or PET, which produce three-dimensional images that show the flow of blood through the coronary arteries and the heart itself. MPI is the most accurate test available for diagnosing CAD early in patients who may be at risk for a heart attack.

myocardial perfusion scan (MPI)

A common cardiac nuclear medicine imaging procedure that creates images of blood-flow patterns within the heart. MPI scans help physicians assess heart function and whether the heart is receiving enough blood and oxygen. MPI scans are created with either SPECT or PET, which produce three-dimensional images.

myocarditis

Also called acute heart dysfunction. An inflammation of the heart muscle usually caused by viral, bacterial, or fungal infections that reach the heart.

N

nanometer

A metric unit of length equal to one billionth of a meter.

nanoparticle

Any microscopic particle less than about 100 nanometers (nm) in diameter. Nanoparticles are unique structures that are designed for specific purpose. Their extremely small size makes them very useful in medical applications where specifically designed particles scan deliver drugs directly into targeted cells and even across the blood-brain barrier.

nanotechnology

The use of extremely small physical structures (100 nanometers or smaller) for a directed outcome. At that size, many physical interactions do not follow the same rules as larger structures. Nanoscale structures that can be extremely useful in the medical field.

National Oncologic PET Registry (NOPR)

In order to determine how best to expand coverage of positron emission tomography (PET) scanning for Medicare cancer patients, the Centers for Medicare and Medicaid Services (CMS) is collecting information on PET scans with this registry.

nerve

A bundle of nerve fibers or axons

nervous system

The collection of approximately 10 billion nerve cells called neurons that conduct, receive and transfer electrochemical impulses. It includes the central nervous system (brain, spinal cord and optic nerves) and peripheral nervous system including nerve roots, nerve plexuses, and nerves throughout the body.

neurodegenerative diseases

Conditions in which nerve cells, called neurons, of the brain and spinal cord cease to function and eventually die, including Parkinson’s disease, amyotrophic lateral sclerosis (ALS), multiple sclerosis, Huntington’s disease, Alzheimer’s disease and other forms of dementia.

neuroendocrine

Relating to the nervous system (the collection of neurons and associated cells that carries electrical impulses between parts of the body) and endocrine system (various glands that secrete hormones or other products directly into the blood). Neuroendocrine cells receive neurotransmitters released by neurons and, as a consequence of this input, release message molecules called hormones into the blood. In this way they bring about an integration between the nervous system and the endocrine system.

neuroimaging

A branch of medical imaging dedicated to imaging the brain.

neuroimaging probes

Imaging agents developed especially for diagnostic imaging of specific areas or functions of the central nervous system.

neuron

Nerve cells that make up the central nervous system. Neurons consist of a nucleus, a single axon that conveys electrochemical signals to other neurons and a host of dendrites that receive incoming signals.

neurotransmission

The constant exchange of messages between neurons. Some neurons send messages in the form of a chemical signal (called a neurotransmitter) and others send an electrical signal. Neurotransmission involves these basic steps:

activation of a neuron

neuron sends a signal (also called an impulse) across the synapse tiny gaps between two neurons

the neurotransmitter binds to the receptor of a receiving cell

during the binding process the neurotransmitter’s message is passed on.

neurotransmitter

Some neurons, the basic working unit of the brain and nervous system, send messages in the form of a chemical signal, or neurotransmitter. The neurotransmitter binds to the receptor of a receiving cell and passes on information in a process called neurotransmission.

non-Hodgkin lymphoma (NHL)

A type of lymphoma, a cancer in the lymphatic system, in which the cells abnormally reproduce, eventually causing tumors to grow.

non-invasively

A procedure performed without making a surgical incision or inserting a medical instrument into the body.

noninvasive

Without making a surgical incision or inserting a medical instrument into the body. Many nuclear imaging and molecular imaging procedures are noninvasive.

nuclear cardiology

The use of a radiotracer and an imaging device to study physiological processes of the cardiovascular system, primarily the heart. Nuclear cardiology exams can assess how well the heart is pumping, reveal vessel blockages that have resulted in or may cause a heart attack, and identify which areas of the heart muscle were damaged by a heart attack. New radiotracers are being developed that bind to and can demonstrate the build-up of plaque in the arteries.

nuclear functional study

Also called a wall motion study, gated nuclear angiogram or MUGA scan. A nuclear medicine test used to assess the heart’s pumping function. This study is most often used to measure the function of the left ventricle (LV), which is the major pumping chamber of the heart. For the test, the patient’s own red blood cells are tagged with a radioactive material called Technetium (Tc-99m) and then injected back into the bloodstream. A gamma camera detects the radioactive red blood cells as they circulate through the heart and measures the timing of cell movement during the contraction and relaxation phases of the heart

nuclear medicine/nuclear imaging

The use of very small amounts of radioactive materials (called radiopharmaceuticals or radiotracers) to evaluate molecular, metabolic, physiologic and pathologic conditions of the body for the purposes of diagnosis, therapy and research. Nuclear medicine procedures can often identify abnormalities very early in the progress of a disease — long before many medical problems are apparent with other diagnostic tests.

nucleus

The core of an atom that contains particles known as protons and neutrons. Electrons orbit around the atomic nucleus. Depending on the arrangement of particles within the atom, it may be extremely stable, or it may be unstable, in which case the atom can gain or lose particles, generating radioactivity.

O

obsessive-compulsive disorder

An anxiety disorder characterized by unreasonable thoughts and fears (obsessions) that lead to repetitive behaviors or compulsions.

opacity

The degree to which light or electromagnetic radiation is permitted to pass through a material.

optical imaging

A molecular imaging procedure in which light-producing molecules designed to attach to specific cells, such as cancer cells or brain chemicals, are injected into the patient’s bloodstream. Imaging is then performed using devices that are able to detect these molecules inside the body. The two major types of optical imaging are bioluminescent imaging, which uses a natural chemical, such as luciferase, the substance that enables fireflies to glow, to trace the movement of certain cells or to identify the location of specific chemical reactions within the body and fluorescence imaging, which uses proteins that produce light when activated by an external light source such as a laser.

ovary

Part of a woman’s reproductive system. The ovaries produce eggs and the hormones estrogen and progesterone. Through the process of ovulation, the ovaries release eggs into the fallopian tubes, where they travel to the uterus, or womb. Pertaining to the ovaries.

P

pancreas

A gland that makes enzymes that help the body break down and use nutrients in food. It also produces the hormone insulin and releases it into the bloodstream to help the body control blood sugar levels.

papillary thyroid cancer

One of several types of differentiated thyroid cancer; it may be treated with I-131 radiotherapy.

Parkinson’s disease

Parkinson’s disease (PD) is a brain disorder that leads to shaking (tremors) and difficulty with walking, movement, and coordination. PD encompasses a variety of syndromes, all of which are progressive and degenerative. Parkinsonian syndromes are characterized by dysfunctional motor control, which is caused by a loss of dopamine- and noradrenaline- producingneurons that send signals that help coordinate muscle movement.

peripheral artery disease (PAD)

A condition in which the blood vessels that supply the legs and feet with oxygenated blood become narrow and hard, leading to decreased blood flow to the lower extremities and causing injury to nerves and other tissues.

PET

Positron emission tomography involves the use of an imaging device (PET scanner) and a tiny amount of radiotracer that is injected into the patient’s bloodstream. A frequently used PET radiotracer is fluorodeoxyglucose (FDG), which the body treats like the simple sugar glucose. It usually takes between 30 and 60 minutes for the FDG distribution throughout the body to become fixed. PET-CT is a combination of PET and computed tomography (CT) that provides detail on both the anatomy and function of organs and tissues. This is accomplished by superimposing the precise location of abnormal metabolic activity (from PET) against the detailed anatomic image (from CT).

PET-CT

A combination of positron emission tomography (PET) and computed tomography (CT) that produces special views of the body. A combined PET-CT study is able to provide detail on both the anatomy and function of organs and tissues. This is accomplished by superimposing the precise localization of abnormal metabolic activity (from PET) against the detailed anatomic image (from CT).

pharmacodynamics

The study of the way drugs effect a living organism including the relationship between size of dose and the effect of the drug.

pharmacogenetics

The study of how a body reacts to a drug based on the individual’s genetic make-up.

pharmacokinetics

The study of how living tissues process drugs, i.e. alter their chemical make-up as a drug is absorbed, distributed, metabolized and excreted. By tagging a drug with a probe or tracer before it is introduced into the body, molecular imaging allows researcher to follow a drug as it progresses through a living system.

pharmacological stress test

Various stress tests involve walking on a treadmill or other exercise in order to assess the electrical activity of the heart while under stress and while at rest. Patients who are unable to exercise may receive an injection of a medication that will make the heart beat fast as it would during exercise.

pharynx

A hollow tube about five inches long that begins behind the nose and leads to the esophagus (the tube leading to the stomach) and the trachea (the tube that leads to the lungs). The pharynx has three parts: the upper part behind the nose called the nasopharynx; the middle called the oropharynx including the soft palate, base of the tongue, and tonsils; and the hypopharynx at the lower end. Part of the respiratory system.

photodynamic therapy

A treatment for melanoma in which a chemical is applied to the skin and exposed to a light source.

photon

The smallest unit of light, or electromagnetic radiation.

Pick’s disease

A type of frontotemporal dementia, which is a group of rare brain disorders that involves the shrinking or atrophy of tissues in the frontal and temporal lobes of the brain.

plaque

A buildup of fat, cholesterol and other substances that accumulates in the walls of the arteries.

plaque, beta-amyloid

Fragments of a protein (amyloid) normally found in the body, that clump together and form abnormal clusters in the spaces between neurons, or brain cells. Scientists believe beta-amyloid plaque plays a role in Alzheimer’s disease.

positron

A particle with the same mass as an electron but the opposite charge. Positrons are emitted in the natural decay of 18F-fluorodeoxyglucose (FDG), an imaging agent used in PET scanning.

positron emission mammography (PEM)

A high-resolution PET scanner designed specifically for breast cancer detection. PEM works much like PET scanning: the patient is injected with a very small amount of a radiotracer such as 18F-fluorodeoxyglucose (FDG), which travels through the body and is absorbed by breast tissue. The breast is then imaged with detectors mounted on compression paddles similar to those used in traditional mammography. Working with a computer, the scanner creates three-dimensional images showing the distribution of the radiotracer in the breast. Because highly active cancer cells absorb more glucose than normal cells, these cells appear brighter on PET scans.

positron emission tomography (PET)

PET involves the use of an imaging device (PET scanner) and a radiotracer that is injected into the patient’s bloodstream. A frequently used PET radiotracer is 18F-fluorodeoxyglucose (FDG), a compound derived from a simple sugar and a small amount of radioactive fluorine. Once the FDG radiotracer accumulates in the body’s tissues and organs based on the rate of sugar use. The PET scanner creates three-dimensional images that show how the FDG is distributed in the area of the body that provides important information on the cellular activity.

post-traumatic stress disorder (PTSD)

A mental health condition that is triggered by a terrifying event. Symptoms include flashbacks, nightmares and severe anxiety, as well as uncontrollable thoughts about the event.

ProstaScint® scan (PSMA Study)

Also called a prostate-specific membrane antigen (PSMA) study. A diagnostic imaging test that allows physicians to locate and determine the extent of prostate cancer in patients who are newly diagnosed prostate cancer, who have had their prostate gland removed or who have an increase in prostate-specific antigen (PSA). The study involves a special molecule called a fragmented monoclonal antibody developed in a laboratory and designed to bind to the prostate-specific membrane antigen on cancer cells. This antibody is paired with a radioactive material called Indium-111 that can be detected by a gamma camera. When injected into the patient’s bloodstream, the radioactive antibody attaches to cancer cells and the gamma camera produces three-dimensional images of the tumor and its location inside the body.

prostate gland

A gland near a man’s bladder and urethra that secretes a thin fluid that is part of semen.

prostate-specific antigen (PSA)

A protein produced by the cells of the prostate gland that is present in small quantities in the blood of normal men but often elevated in the presence of prostate cancer or other prostate disorders.

prostate-specific membrane antigen (PSMA) study

A molecular imaging tool used to detect prostate cancer cells in the body.

prostatectomy

The surgical removal of part or all of the prostate gland.

R

radiation therapy

The use of high-energy waves or particles of radiation to kill cancer cells and shrink tumors.

radioactivity

The spontaneous decay or disintegration of an unstable atomic nucleus accompanied by the emission of radiation.

radioimmunoscintigraphy (RIS) (monoclonal antibody imaging)

The use of a laboratory-developed molecule called a monoclonal antibody that is designed to attach to specific cancer cells. Once the monoclonal antibody is combined, or labeled, with a radioactive atom and injected into the patient, single-photon emission computed tomography (SPECT) imaging is performed, creating three-dimensional images of the tumor.

Radioimmunotherapy

Radioimmunotherapy (RIT) is a personalized cancer treatment that combines radiation therapy with the precise targeting ability of immunotherapy, a treatment that mimics cellular activity in the body’s immune system.

In immunotherapy, scientists create monoclonal antibodies in a laboratory that are designed to recognize and bind to the antigen of a specific cancer cell. In RIT, the monoclonal antibody is paired with a radioactive material. When injected into the patient’s bloodstream, theantibody travels to and binds to the cancer cells, allowing a high dose of radiation to be delivered to the tumor. Because the antibodies are designed to attach only to very specific types of cells, radioimmunotherapy maximizes the radiation that can be delivered to the diseased tissue and minimizes the amount of radiation to which healthy tissue is exposed.

radioiodine

Also called radioactive iodine. The radioisotope of iodine, a naturally occurring non-metallic element that is used in molecular imaging and treatment. Two forms have medical purposes: I-123 is used as a radiotracer for imaging the thyroid and I-131 is used both as a radiotracer and as a therapeutic agent for thyroid cancer.

radioisotope

A radioisotope is a radioactive version of an element. Radioactive elements differ from the stable versions of the same element in that they have either more or fewer neutrons. For example all forms of carbon have the same number on protons (six), but the most common form has six neutrons as well. Forms with five (11C), seven (13C) and eight (the famous 14C) neutrons are radioactive. Some radioisotopes have very long half-lives. For example, the half-life of 14C is 5700 years, making it useful for dating organic materials. And some have very short half-lives: the half-live of 11C is only 20 minutes. There is no chemical difference between the way the radioactive and non-radioactive versions of an element react. The fact that there is no difference allows the radioactive versions of the element to be substituted for the non-radioactive versions to produce a tracer. This principal can also be applied to therapy. Iodine, which was the first element used in nuclear medicine, is used exclusively by the thyroid gland. If a radioactive isotope of iodine is introduced into the body, it will be taken up by the thyroid gland in exactly the same way as non-radioactive iodine. A gamma camera can then be used to determine how well the thyroid is working. Similarly, a large dose of radioactive iodine can be used to treat thyroid cancer by delivering a tumor-killing radiation dose directly to the cancerous tissue.

radiopharmaceutical

A type of imaging agent used in nuclear medicine, a branch of molecular imaging. It is a compound consisting of a drug and a small amount of radioactive material that localizes in specific organs or areas of the body and can be detected by an imaging device.

radiotracer

A type of imaging agent used in nuclear medicine, a branch of molecular imaging. It is a compound consisting of a drug and a small amount of radioactive material that localizes in specific organs or areas of the body and can be detected by an imaging device.

re-staging

A re-evaluation of the extent of disease, after a round of treatment, that provides the basis for ongoing management.

rectum

The lower section of the large intestine or colon that ends in the anus and acts as storage area for fecal waste.

reporter-gene systems

The use of engineered genes that are designed to adhere to specific cells in body that may be detected by molecular imaging technologies.

risk-stratification

Activities such as lab and clinical testing used to determine a person’s risk for suffering a particular condition, such as coronary artery disease, and the need, or lack thereof, for preventive intervention.

S

sarcoma

A malignant or cancerous tumor that occurs in the connective tissues of the body including the bones, cartilage, tendons and soft tissues.

schizophrenia

A long-term mental disorder of a type involving a breakdown in the relation between thought, emotion, and behavior, leading to faulty perception, inappropriate actions and feelings, withdrawal from reality and personal relationships into fantasy and delusion, and a sense of mental fragmentation.

sentinel lymph node

The first few lymph nodes into which a tumor drains and those most likely to contain cancer cells if the tumor has metastasized or spread.

sentinel node biopsy

A surgical procedure used to determine if cancer has spread beyond a primary tumor into the lymphatic system. It is most commonly used to evaluate melanoma and breast cancer, as a alternative to an axillary lymph node dissection. The procedure involves using molecular imaging is used to identify the sentinel, or first few, lymph nodes into which a tumor drains and those most likely to contain cancer cells if the disease has metastasized, or spread. Only the sentinel nodes are surgically removed, which results in fewer complications and side effects for the patient, including lymphedema.

Since molecular imaging works at the cellular and molecular level, it can provide accurate information about disease processes at a very early stage. Molecular imaging provides personalized information about an individual’s specific disease and how that disease may react or has reacted to specific treatments.

SPECT

SPECT stands for “single-photon emission-computed tomography.” A SPECT scan uses a gamma camera to detect radioisotopes that emit high-energy radiation. The gamma camera works with a computer to create three-dimensional images of the distribution of the tracer in the body. SPECT is most often used in cardiology to provide information about blood flow through the heart muscle that can be used to diagnose heart disease. It is also used for brain and bone scans and to detect infection and certain types of tumors.

spleen

An organ located on the left side of the abdomen near the stomach that is part of the lymphatic system. It produces lymphocytes, filters the blood, stores blood cells and destroys old blood cells.

stage

A measure of the extent of disease present in the body.

stress perfusion study

A type of study in which images of a patient’s heart at rest are compared to the images of the heart immediately after exercise to determine the effect of physical stress on coronary blood flow. The stress perfusion study assesses heart function and whether the heart is receiving enough blood and oxygen. The test is performed with either SPECT or PET, which produce three-dimensional images that show the flow of blood through the coronary arteries and the heart itself.

stroke

A loss of brain function due to an interruption in the flow of blood to the brain due to a clot blocking a blood vessel or the rupture of an artery in the brain.

sudden cardiac death

Also called sudden cardiac arrest. A condition in which the heart suddenly and unexpectedly stops beating. Blood stops flowing to the brain and other vital organs and without treatment, death will occur within minutes.

synapse

A junction between two nerve cells or neurons where information is transferred from one cell to another in a process called neurotransmission. Impulses traveling down one nerve cell cause the release of a neurotransmitter which diffuses across the gap where it is received by another cell.

systolic

Refers to the contraction of the heart muscle that pumps or ejects blood out of the heart. In systolic heart failure, the heart no longer pumps out enough blood to meet the body’s needs.

T

tachycardia

A type of arrhythmia, or heart rhythm problem, in which the heart beats too fast.

Technetium-99m-Sestamibi (MIBI)

Also referred to as Tc-99m-Sestamibi (MIBI). A radiotracer used in breast-specific gamma imaging to detect additional lesions missed by mammography and physical exam and cancers that are difficult to detect using mammography. The radiotracer is injected into the patient’s bloodstream and accumulates in malignant tissue where it can be detected by a special gamma camera.

Technetium-99m-sulfur-colloid

Also called Tc-99m-colloid. A radiotracer used in lymphoscintigraphy that can be detected by a gamma camera to help identify the first, or sentinel, lymph nodes into which a melanoma site drains.

thymus

An organ located in the upper portion of the chest cavity just behind the sternum that produces T lymphocytes, white blood cells that fight infection and destroy abnormal cells as part of the body’s immune defense system.

thyroid

An organ located at the base of the throat that makes hormones that help control heart rate, blood pressure, body temperature and weight.

thyroid gland

One of nine endocrine glands in the body, located in front of the neck just below the Adam’s apple. The gland is shaped like a butterfly, with two lobes on either side of the neck connected by a narrow band of tissue. The gland produces thyroid hormones that set the rate at which the body carries on its necessary functions, also known as the metabolic rate.

tomography, tomographic reconstruction

Tomographic reconstruction is a technique that uses a series of two-dimensional images to create a three-dimensional image. For example, a computed tomography (CT) scanner acquires a series of cross-sectional x-rays, which are combined (using tomographic reconstruction algorithm software) into a three-dimensional image of the body that can be viewed from any direction.

transient ischemic attack

A temporary loss of blood supply to tissues in the brain, also called a ‘mini-stroke.’ It can cause brief symptoms such as dizziness, slurred speech, weakness or numbness but no permanent damage.

translational medicine

Translational medicine is the process of moving basic laboratory research into mainstream medical practice. Translational medicine focuses on the necessary steps—including patient testing and clinical trials—that will ensure safety before a technique can be used on patients in clinical practice.

tumor

An abnormal growth of tissue that results from excessive cell division that can be benign or malignant (cancerous).

tumor marker

The presence of a substance either released by cancer cells into the blood or urine or that is created by the body in response to cancer cells. Elevated levels of these substances may indicate that disease is present. Tumor markers are also used by molecular imaging technologies to detect disease, evaluate how well a patient has responded to treatment or to check for a tumor recurrence.

U

ultrasound

Essentially an anatomical imaging technology that uses sound waves to create images of tissue within the body. It can be a molecular imaging technique when used in conjunction with targeted microbubbles.

urethra

The duct or tube from the bladder through which urine passes as it leaves the body.

uterus

Also called the womb. The hollow, muscular organ in a woman’s lower abdomen in which a fertilized egg implants and matures through pregnancy. Pertaining to the uterus.

V

ventricular remodeling

Changes in size, shape, and function of the heart as a result of an injury to the heart, such as a heart attack. The process typically leads to a progressive decline in the performance of the left ventricle, the heart’s main pumping chamber.

X

x-ray

A noninvasive medical test that helps physicians diagnose and treat medical conditions. Imaging with x-rays involves exposing a part of the body to a small dose of ionizing radiation to produce pictures of the inside of the body.

Y

yttrium-90 labeled octreotide

A radiopharmaceutical being evaluated in clinical trials as an alternative to radioiodine for patients whose thyroid cancer is not responsive to I-131 radiotherapy with iodine.